Ti-Zr催化剂对NaH/Al复合物可逆储氢特性的影响

采用机械球磨(NaH/Al+Ti)和(NaH/Al+Ti-Zr)复合物的方法加氢制备了NaAlH4配位氢化物, 系统研究了Ti、Ti-Zr催化剂以及不同加氢条件对其可逆储氢行为的影响. 结果表明, 对于NaH/Al体系的吸放氢性能, 共掺金属Ti粉/Zr粉的催化作用比单独掺金属Ti粉的催化作用要好. 随着加氢温度从85 ℃上升到140 ℃, 体系的吸氢容量先增后减, 并在120 ℃时达到最大值; 同时, 发现共掺Ti-Zr催化剂的复合物具有最佳的储氢性能, 在120和85 ℃时的吸氢量分别为4.61%和3.52%(w), 比仅掺Ti 催化剂的复合物分别高出0.40%和0.70%(w)的吸氢量. 随着加氢压力的增大, (NaH/Al+Ti-Zr)复合物的吸氢性能随之提高. XRD和DSC分析结果表明, NaAlH4体系的放氢过程明显发生两步分解反应, 共掺Ti-Zr催化剂的复合物储氢性能优于单独掺Ti 催化剂的原因是, 共掺催化剂能有效改善NaAlH4体系吸放氢反应的动力学性能,并降低体系的放氢温度.

Influence of Ti-Zr Catalysts on Reversible Hydrogen Storage Characteristics of NaH/Al Composite

The NaAlH4 complex hydride was prepared by hydrogenation of the ball-milled (NaH/Al+Ti) and (NaH/Al+Ti-Zr) composites. The influences of Ti and Ti-Zr catalysts, different hydriding temperatures and pressures on its reversible hydrogen storage behaviors were investigated. It was found that the catalysis of Ti-Zr powders as co-catalysts on the dehydriding/hydriding characteristics of NaH/Al was better than that of Ti alone as catalyst. As the hydriding temperature increased from 85 ℃ to 140 ℃, the hydrogen absorption capacity increased first and then decreased, and reached the highest value at 120 ℃. The composite co-doped with Ti-Zr catalysts had the best reversible hydrogen storage properties, its hydrogen storage capacities were 4.61%(w) at 120 ℃ and 3.52%(w) at 85 ℃, which were 0.40% and 0.70%(w) higher than that doped with Ti alone as catalyst in the same hydriding condition, respectively. The hydrogen storage performance of (NaH/Al+Ti-Zr) composite was enhanced with the increase of hydriding pressure. XRD and DSC analyses showed that the dehydriding process of NaAlH4 system took place in two steps. The composite co-doped with Ti-Zr catalysts could improve the dehydriding/hydriding kinetics of NaAlH4 systemand reduced its dehydriding temperature. That was the main reason of the hydrogen storage characteristic of the composites co-doped with Ti-Zr catalysts better than that doped with Ti catalyst alone.